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THERMODYNAMICS SPECIFIC LEARNING OBJECTIVE At the end of the session the student should be able to explain: •Energy •The first law of thermodynamics •Entropy •Free energy Thermodynamic In Chemistry System In Living System THERMODYNAMICS Thermodynamic is the law that formulated from observation on conversion of energy from one form to the other. i.e. transduction What is the energy? 1. Energy is a much used term, but it represents a rather abstract concept. 2. Energy is usually defined as the capacity to do work. 3. Chemist define work as directed energy change resulting from a process The type of Energy 1. Kinetic energy 2. Radiant energy 3. Thermal energy 4. Chemical energy 5. Potential energy Definition of type energy 1. Kinetic energy – the energy produced by a moving object 2. Radiant energy : comes from the sun (solar energy) and is Earth’s primary energy source. Solar energy heats the atmosphere and Earth’s surface, stimulates the growth of vegetation through the process known as photosynthesis, and influences global climate patterns. continued The Activated Complex form the reaction: A+B AB# P Definition of type energy 3.Thermal energy is the energy associated with the random motion of atoms and molecules. 4. Chemical energy is stored within the structural units of chemical substances; its quantity is determined by the type and arrangement of atoms in the substance being considered. 5. Potential energy is energy that is also available by virtue of an object’s position. Conclusion of Energy • All forms of energy can be interconverted (at least in principle) from one form to another Scientists have concluded that energy can be neither destroyed nor created. • Thermodynamic Law THERMODYNAMICS Thermodynamic I is the law of conservation of energy Thermodynamic I Work Thermodynamic II Work and heat are not state functions Thermodynamic III Heat • The relationship between chemical energy and other forms of energy, with examples. Energy change in chemical reactions Almost all chemical reactions absorb or produce (release) energy, generally In the form of heat. • Heat is the transfer of thermal energy between two bodies that are at different temperatures. Although ”Heat” itself implies the transfer of energy, we customarily talk of ”heat absorbed” or ”heat released” when describing the energy changes that occur during a process. Energy changes associated with chemical reactions System Surroundings SYSTEM AND SURROUNDING System we mean that the part of the world we are investigating. Surrounding we Three type of systems be Open Close mean everything else Surrounding Isolated system System be open • Two of this examples are the examples of open system: 1.e.g. in the living organism, which takes up nutrients, releases the waste products, and generates work and heat. 2.An example in body, the body takes up nutrient, and then release urine which contains toxin, carbon dioxide, and so on. System be closed Example of close system: • An example of close system is living of an microorganism, it was sealed inside a perfectly insulated box, it will, together with the box, constitute a closed system. HEAT q, to be the manner of energy transfer that results from a temperature difference between the system and its surrounding Positive and negative sign of heat Heat input to a system is considered a positive quantity Heat evolved by a system is considered a negative quantity. WORK w, to be the transfer of energy between the system of interest and its surroundings as a result of existence of unbalanced forces between two. Positive and negative sign of work If the energy of the system is increased by the work, we say that work is done on the system by surroundings, and we take it to be a positive quantity if the energy of the system is decreased by the work, or the system does work on the surroundings, or that work is done by the system, and we take it to be a negative quantity • The effect of work is equivalent to the raising or lowering of mass in the surroundings. • Work is done by the system because the mass is raised work is done on the system because the mass is lowered. ENERGY Energy is a state function It is a property that depends only upon the state of the system, and not upon how the system was brought to that state, or upon the history of the system. Thermodynamic I study of conservation of energy The first law of thermodynamic •∆U=q+w which is essentially a statement of the law of conservation of energy. Where : 1. The term ∆ U represents the change of internal energy of the system, 2. q is the thermal energy (heat) added to the system, and w is the work done on the system. The chemical reactions that need energy 1. The Photoelectric Effect this is mystery in physics. Experiments had already demonstrated that electrons were ejected from the surface of certain metals exposed to light of at least a certain minimum frequency. Einstein suggested that a beam of light is a stream of particles. These particles of light are called photons. Using Planck’s quantum theory of radiation as a starting point, Einstein deduced that each photon must possess energy E, given by the equation : E = hv In which v is the frequentcy of light and h is Planck’s constant The equation of E = hv E = hv E = KE + BE hv = KE + BE in which : * KE is the kinetic energy of the ejected electron and * BE is the binding energy of the electron in the metal The energies that the electron in the hydrogen atom • En = – RH 1 n2 • In which RH, the Rydberg constant, has the value 2.18 x 10-18 J • The number n is an integer called the principal quantum number; it has the value n = 1, 2, 3,…. Strength of Covalent Bond The Strength of Covalent Bond is defined by the amount of energy needed to break it. A quantitative measure of stability of a molecule is its bond dissociation energy (or bond energy). For example: H2(g) H(g) + H(g) H = 436.4 kJ HCl(g) H9g) + Cl(g) H = 431.9 kJ Covalent Bond in Organic Compounds STRUCTURE SATURATED: Bonding : are formed by overlap of two atomic orbitals, each of which contains one electron UNSATURATED : and bonding. bonding (pi) bond ENTHALPY • The enthalpy of a system, which has the symbol H, is that of Heat content (heat of reaction) and is measure of the change in total bonding energy during a reaction. It is defined mathematically as : H = U + PV; H is a function of state The standard enthalpy change for any reaction (∆H0rxn)can determine by using standard enthalpies of formation (∆H0f) and Hess’s Law CONSTANT PRESSURE PROCESSES • Most processes occur in the open at one atmosphere pressure. In these cases, P1 = P2 = P, say, and • ∆H = ∆U + P ∆V Positive and negative sign of Enthalpy • ∆ H has a negative sign for an exothermic change (heat is released), is mean the bonds in the products are stronger (more stable) than the bonds in the reactants. • ∆ H has a positive sign for an endothermic change (heat is absorbed), is mean the bonds in the products are weaker (less stable) than the bonds in the reactants. HESS’S LAW The principle of constant heat summation, often known as Hess’s Law, is thus seen to lead directly from the fact that H is a function of state. Hess’s Law be valid for : ∆r H˚ or ∆f H˚, ˚ = all reactants and products are in • their standard states. f = formation standard enthalpies of formation Pº = 1 atmosphere, and temperature 25ºC or 298.15°K • This idea is immensely powerful, because it enables Hº298 values to be determined for any reaction, as long as the H of formation are known for each reactant and product. • ∆r H = H prod – H react Example No. 1 : • Consider the following two chemical equations. • 1. C(s) + ½ O2 (g) CO (g) ∆r H (1) = -110.5 kJ 2. CO (g) + ½ O2 (g) CO2 (g) ∆r H (2) = -283.0 kJ How many Joule ∆r H (3) = ….? For below equation C (s) + O2 (g) CO2 (g) ∆r H (3) = ...? Example No. 2 : 2 P(s) + 3 Cl2(g) 2 P(s) + 5 Cl2(g) 2 PCl3(l) ∆rH (1)= -640 kJ 2 PCl5(s) ∆rH (2)= -887 kJ Please calculate the value of ∆r H for below equation PCl3(l) + Cl2(g) PCl5(s) ∆r H (3) = .....? • Please you make the application of Hess’s Law, consider the use of solution No. 2: 2 P(s) + 3 Cl2(g) 2 P(s) + 5 Cl2(g) 2 PCl3(l) ∆rH (1)= -640 kJ 2 PCl5(s) ∆rH (2)= -887 kJ Please calculate the value of ∆r H for below equation PCl3(l) + Cl2(g) PCl5(s) ∆r H (3) = .....? • Please you make the application of Hess’s Law, consider the use of A. – 247 kJ B. + 247 kJ C. – 124 kJ D. + 124 kJ E. – 1527 kJ. Spontaneous Changes The process tends to occur or not Two driving forces in nature 1. The towards minimization of energy is one such directing influence, but there is also a tendency for material to become more physically disorganized. 2. The tendency for entropy to increase is nature’s second driving force. ENTROPY • The symbol of entropy = S a thermodynamic function of state NATURAL OR IRREVERSIBLE PROCESS • The entropy of system and surroundings together increases during all natural or irreversible process; • ∆ Ssystem + ∆ Ssurrounding = ∆ Suniverse > 0 REVERSIBLE PROCESS • For reversible process, the total entropy is unchanged; • ∆ Ssys + ∆ Ssur = ∆ Suniverse = 0 CYCLIC PROCESSES • For a cyclic process, a process in which the final state is the same as the initial state, ∆S = 0 Changes of entropy with temperature • ∆ S = S2 – S1 = CP ln T2/T1 (P constant) • ∆ S = S2 – S1 = CV ln T2/T1 (V constant) Absolute entropy The third Law of Thermodynamics All truly perfect crystals at absolute zero temperature have zero entropy. FREE ENERGY Gibbs Free Energy The Gibbs energy determines the direction of a Spontaneous Process for a System at Constant Pressure and Temperature G is function of state Gibbs free energy, G,. It is a function of state which provides possible or not a change of any kind will tend to occur. The value of ∆ G • For a favorable reaction, ∆G has a negative value, meaning that energy is released to the surroundings Exergonic • For a unfavorable reaction, ∆G has a positive value, meaning that energy is absorbed from the surroundings Endergonic REACTION AT CONSTANT TEMPERATURE & PRESSURE dG ≤ 0 (constant T and P) The quantity G is called the Gibbs energy Value of G in a system at constant T and P • The Gibbs energy will decrease as the result of any spontaneous processes until the system reaches equilibrium, where d G = 0. • The Gibbs free energy is defined as: • G = H - TS RELATIONSHIP BETWEEN THE PROCESSES WITH GIBB’S FREE ENERGY Spontaneous processes, that is, those with negative ∆ G values, are said to be exergonic; they can be utilized to do work. Processes that are not spontaneous, those with positive ∆ G values, are termed endogonic; they must be driven by the input of free energy. Processes at equilibrium, those in which the forward and backward reactions are exactly balance, are characterized by ∆ G = 0. Thermodynamic In Chemistry System In Living System What was The Thermodynamic Studied in Living System? • • • • • • • • Thermodynamic In Living System 1. ∆ H (heat) 2. ∆ S (the extent of disorder of the system) 3. ∆ G (Gibbs change in free energy that proportion of the total energy change in a system, that is available for doing work) Thermodynamic In Living System • Under the conditions of biochemical reactions, • 1. ∆ H (heat) is approximately equal • to ∆ E, the total change in internal • energy of the reaction, • ∆ G = ∆ H – T ∆S, become: • ∆ G = ∆ E – T ∆S What is the difference between chemical reaction in nonbiologic systems and in biologic systems? Nonbiologic systems may utilize heat energy to perform work, but biologic systems are essentially isothermic and use chemical energy to power living processes. ATP (Adenosine Triphosphate): The Primary Energy Carrier) • Certain bonds in ATP save the energy released during the oxidation of carbohydrates, lipids, and proteins. • The ATP molecules act as energy carries, and deliver the energy to the parts of the cell where energy is needed to power muscle contraction, biosynthesis, and other cellular work. Energy source in the body ATP plays a central role in the transference of free energy from the exergonic to the Endergonic processes. It serves as a carrier of chemical energy between high energy phosphate donors and low energy phosphate acceptors Structure of ATP Energy source in the body ATP consists of adenine (a purine), ribose and three phosphate groups, out of which the two terminal phosphate groups being anhydride bonds are the high energy groups Structure of ATP Energy change in chemical reactions Almost all chemical reactions absorb or produce (release) Energy. The standard free energy, i.e. ∆ G0’ of hydrolysis of ATP 1. ATP + H20 ADP + Pi ∆ G0’ = -7.3 kcal/mol used for doing work 2. ATP + H20 AMP + PPi ∆ G0’ = -7.7 kcal/mol Chemical reaction can use up, or produce useful energy. Exergonic reactions produce an energy output (ΔG = - means that the process is not favorable) Endergonic reactions require an energy Input (ΔG = + the criterion for a favorable process in a nonisolated system, at constant temperature and pressure) Biochemical system couple these energy yielding (exergonic: unstable to stable) with energy requiring (endergonic: stable to unstable) to make cellular metabolism work. Energy transfer in the body The working cell • The chemical reactions within cells are accompanied by changes in energy. • Cells accomplish their tasks by coupling energy-requiring reactions with energy-producing reactions Protein + ATP Pro-phosphate complex + ADP (protein is phosphorylated) What is the reaction called, if a reaction between solute and solvent needs heat? • • • • • A. exergonic reaction B. endergonic reaction C. exothermic reaction D. endothermic reaction E. kinetic reaction • The reaction of glucose become to glucose-6-phosphate as follows: • Pi + glucose glucose-6-P + H2O • ΔG0 = +13.8 (kJ.mol-1) • ATP + H2O ADP + Pi • ΔG0 = -30.5 (kJ.mol-1) ATP + glucose ADP + glucose-6-P • ΔG0 = -16.7 (kJ.mol-1) What is the reaction above called? A. exergonic reaction B. endergonic reaction C. exothermic reaction D. endothermic reaction E. kinetic reaction Energy transfer in the body • Phosphoryl-transfer Reactions • R1-O-PO32- + R2-OH R1-OH + R2-O-PO32• Are of enormous metabolic significance. Some of the most important reactions of this type involve the synthesis and hydrolysis of ATP: • ATP + H2O ADP + Pi • ATP + H2O AMP + PPi • For examples: next slide Continuation: Energy transfer in the body • The metabolism of glucose is its conversion to glucose-6-phosphate : • Endergonic half-reaction 1: • Pi + glucose glucose-6-P + H2O ΔG0 = +13.8 (kJ.mol-1) • Exergonic half reaction 2: • ATP + H2O ADP + Pi • ΔG0 = - 30.5 (kJ.mol-1) ATP + glucose ADP +glucose-6-P • ΔG0 = -16.7 (kJ.mol-1) Exergonic Active transport: An energy-requiring process involving the movement of substances across a membrane • High muscle activity: 1. relaxed muscle + ATP Contracted muscle + ADP + Pi 2. ADP + phosphocreatinine ATP + creatine • Low muscle activity: 1. Catabolic energy + ADP +Pi ATP 2. ATP + Creatine ADP + Phosphocreatine THERMODYNAMICS OF LIVE 1. Living organism are open system and therefore can never be at equilibrium. 2. The free energy from this process is used to do work and to produce the high degree of organization characteristic of life. 3. Living system must maintain a nonequilibrium state for several reasons. For example: the ATP-generating consumption of glucose. Alterations in Body Temperature • FEVER AND HYPERTHERMIA: • Fever: • Is an elevation of body temperature above the normal circadian range as the result of a change in the thermoregulatory center located in the anterior hypothalamus. • A normal body temperature is ordinarily maintained, despite environmental variations, through the ability of the thermoregulatory center to balance heat oproduction by tissues (notably, muscles and the liver) with heat dissipation. Continuation: • With fever, the balance is shifted to increase the core temperature. • Hyperthermia: • Is an elevation of body temperature above the hypothalamic set point due to insufficient heat dissipation (e.g. in association with exercise perspirationinhibiting drugs, or a hot environment) the topic in Lab activity (salicylat poisoning) Summary References: 1. Warn, J.R.W., 1999, Concise Chemical Thermodynamics, Second Edition, Stanley Thornes Ltd., United Kingdom. 2. McQuarrie, D.A., Simon, J.D., 1997, Physical Chemistry a Molecular Approach, University Science Books, Sausalito.